Malignant tumors developed in the food passing, digesting, and absorbing organs such as the esophagus, stomach, duodenum, small intestine, and large intestine are classified into digestive cancers that are one of serious disorder groups, having a large number of patients along with lung cancer and breast cancer. Among them, large intestine cancer is ranked high in the number of occurrences and fatalities, regardless of the region of Japan, United States, or Europe, or the patient sex of male or female (the annual number of patients in each region: 100,000 or more). Stomach cancer has such a specificity that the occurrence frequency is high in Japan (the annual number of patients: about 100,000), but an annual number of patients as large as 10,000 is reported in United States or European countries. Esophagus cancer has a smaller number of incidence as compared with large intestine cancer and stomach cancer, but is ranked at 6th of the list for male Japanese (the occurrence ratio of male:female is 6:1), and over 10,000 of people suffer every year. Although the number of patients and fatalities of digestive cancer is large, but if the cancer is in an early stage in which the cancer remains in polyp and mucosa, the cancer can be cured by endoscopic mucosal resection.
However, when the lesion outstretches the large intestine wall, the intestine is surgically removed. Further, if the detection of the cancer is delayed and there is a distant metastasis, the cancer is treated by combining chemotherapy with surgical therapy. As a chemotherapy drug against large intestine cancer, promising new drugs such as Oxaliplatin, a platinum-based drug and Avastin, an antibody drug have been developed in recent years. However, these drugs do not provide a sufficient therapeutic outcome.
The best therapy for these digestive cancers is early detection and focal site resection. Cancer develops from the mucosal side. In the case of early cancer where the focal site remains in the mucosa, endoscopic mucosal resection is an adequate treatment. If the application of this treatment expands, a number of plus factors including reduction of patient burden, improvement of therapeutic outcome, and improvement of medical economics would be expected.
However, the present diagnosis with an endoscope still stays at the stage where only a tumor as large as 1 to 2 cm can be detected, with which a risk of metastasis to multiple organs increases abruptly.
In view of the circumstances as described above, a diagnostic marker that can stain specifically cancer cells or tissues has been attempted, and is disclosed, for example, in Patent Document 1.
However, this diagnostic marker is composed of a fluorescence compound bound to an antibody that specifically binds to cancer cells or tissues (or is composed of a fluorescent functional group incorporated into the antibody). The diagnostic marker certainly can stain cancer tissues or their peripheral mucosal tissues. But the diagnostic marker binds to normal tissues to some extent besides the cancer tissues, and also the amount of the fluorescence compound per antibody is small, so that the contrast between the cancer tissues and normal tissues is low, and that the marker does not provide a high diagnostic accuracy.    Patent Document 1: Japanese Patent No. 3669752